1. Field of the Invention
The present invention relates to a liquid crystal display device, and more particularly, it relates to a color filter for use with the liquid crystal display device and a method of making the color filter.
2. Description of the Related Art
The liquid crystal display device has been widely used these days as a display suitable for use with televisions, office automation machines and the like. This is because power consumed by the liquid crystal display device is small and because the device is light in weight and thin in thickness. It is, however, necessary that the liquid crystal display device having these merits can be made larger in size and display images of high quality with respect to color. This causes much attention to be paid to the color filter for use with the liquid crystal display device.
The color filter for use with the liquid crystal display device was conventionally made according to the dying method in which the lithography technique was employed. This dying method includes many lithography steps, thereby causing the cost of manufacturing the liquid crystal display device to be made high. This causes costs of machines each having the liquid crystal display device to be made higher.
Therefore, the print process by which the liquid crystal display device can be manufactured at a lower cost than by the dying method attracted attention. According to the print process, the color filter and the like are made by printing manner. In the case of the color filter made according to the print process, however, foreign matters such as dust are likely to enter into the filter and the surface of the color filter is likely to be undulated. When the surface of the color filter is heavily undulated, it becomes difficult to form the transparent electrode or orientation film on the color filter. This causes the quality of display to become low. The color filter made according to the print process was low in cost but not suitable for practical uses.
Preliminarily-opened Japanese Patent Applications Sho 61-3122 and -3123 disclose a method of making the color filter to eliminate the above-mentioned drawbacks. According to this method, surfaces of colored layers formed by the print process can be polished flat to provide the color filter without giving any influence to the transparent conductive film and the like. More specifically, the method of making the liquid crystal color display element comprises printing opaque portions on the surface of a substrate at a certain interval, printing colored layers between the opaque portions and polishing the colored layers flat.
According to the method disclosed, the surfaces of the colored layers can be polished flat even when the colored layers have unevenness on the surfaces thereof after they are formed, to thereby make a color filter suitable for use with the liquid crystal display device.
Usually, the colored layers of the color filter are made of organic resin including pigment or dye therein and baked at a certain temperature. These colored layers are soft because they are made of resin, and they are a thin film having a thickness of several microns. The technique of directly abrading these colored layers flat becomes more difficult as the size of the substrate on which the colored layers are formed becomes larger. This is because the color layers are likely to be peeled off from the base when they are directly polished. It was therefore impossible to produce the color filter on a mass scale and at a low cost.